I started on a road bike. I almost went for a hybrid... but with wanting to compete in tri's, I decided a road bike was what I needed to start with.
Glad I did! I would have never been able to keep up on club rides, or really competed in tri's on a hybrid.
I also have a tri bike. It's like a road bike, but with a different setup for the handlebars. Good for races, not good for club riding.
It all comes down to what you want to do on your bike. You have to analzye your needs and pick a bike for your needs. Good luck.
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"